1. Field of the Invention
The invention relates to a connecting rod for an internal combustion engine and to an internal combustion engine.
2. Description of the Related Art
DE 10 2010 016 037 A1 and FIG. 1 herein show a known connecting rod of an internal combustion engine having an adjustable compression ratio. With reference to FIG. 1, the connecting rod 10 has a big end bearing eye 11 and a small end bearing eye 12. The big end bearing eye 11 is used to connect the connecting rod 10 to a crankshaft (not shown in FIG. 1) and the small end bearing eye 12 is used to connect the connecting rod 10 to a cylinder piston (not shown in FIG. 1) of the internal combustion engine. The connecting rod 10 is assigned an eccentric adjustment device 13, that has an eccentric (not shown in FIG. 1), an eccentric lever 14 and eccentric rods 15, 16. The eccentric lever 14 has a hole arranged eccentrically with respect to a central point 17 of the small end bearing eye 12 and has a central point 18. The hole in the eccentric lever 14 accommodates the eccentric and a hole in the eccentric accommodates a piston pin. The eccentric adjustment device 13 is used to adjust an effective connecting rod length leff, where the connecting rod length is to be taken to mean the distance between the central point 18 of the hole in the eccentric lever 14 and a central point 19 of the big end bearing eye 11. The eccentric rods 15, 16 can be moved to turn the eccentric body 14 and hence change the effective connecting rod length leff. Each eccentric rod 15, 16 is assigned a piston 20, 21 that is guided movably in a hydraulic chamber 22, 23. A hydraulic pressure prevails in the hydraulic chambers 22, 23 and acts on the pistons 20, 21 assigned to the eccentric rods 15, 16. Thus, repositioning of the eccentric rods 15, 16 is possible or not possible, depending on the quantity of oil in the hydraulic chambers.
Adjustment of the eccentric adjustment device 13 is initiated by action of inertia forces and load forces of the internal combustion engine acting on the eccentric adjustment device 13 during a power stroke of the internal combustion engine. The directions of action of the forces acting on the eccentric adjustment device 13 are constant during a power stroke. Hydraulic oil acts on the pistons 20, 21 and the pistons act on the eccentric rods 15, 16 to assist the adjusting movement. The pistons 20, 21 prevent resetting of the eccentric adjustment device 13 due to variations in the directions of action of the forces acting on the eccentric adjustment device 13. The eccentric rods 15, 16 interact with the pistons 20, 21 and are connected to each end of the eccentric body 14. The hydraulic chambers 22 and 23 in which the pistons 20, 21 are guided can be supplied with hydraulic oil via hydraulic oil lines 24 and 25, starting from the big end bearing eye 11. Check valves 26 and 27 prevent the hydraulic oil from flowing back out of the hydraulic chambers 23 and 24 into the hydraulic lines 24 and 25. A changeover valve 29 is accommodated in a hole 28 in the connecting rod 10. The operating position of the changeover valve 29 determines which of the hydraulic chambers 22 and 23 is filled with hydraulic oil and which of the hydraulic chambers 22 and 23 is emptied, with the direction of adjustment or direction of rotation of the eccentric adjustment device 13 depending thereon. In this arrangement, the hydraulic chambers 22 and 23 are in communication via fluid lines 30 and 31, respectively, with the hole 28 accommodating the changeover valve 29. An actuating means 32, a spring device 33 and a control piston 34 of the changeover valve 29 are shown schematically in FIG. 1, and the operation of these component elements of the changeover valve 29 is known from DE 10 2010 016 037 A1.
As explained above, the hydraulic oil that acts on the pistons 20, 21 guided in the hydraulic chambers 22, 23 is fed to the hydraulic chambers 22, 23, starting from the big end bearing eye 11, via hydraulic lines 24 and 25. The connecting rod 10 engages by means of the big end bearing eye 11 on the crankshaft (not shown in FIG. 1) in such a way that a connecting rod bearing shell 35 is arranged between the crankshaft, namely a crankshaft bearing journal thereof, and the big end bearing eye.
DE 10 2005 055 199 A1 discloses further details of an internal combustion engine with an adjustable compression ratio. More particularly, this prior art discloses inserting the eccentric lever on which the eccentric rods engage into a slot-type aperture in the small end bearing eye. The eccentric lever has a hole with internal toothing and is inserted into the slot-type aperture in the small end bearing eye. The eccentric has external toothing and is inserted into the hole in the eccentric lever. The eccentric and the eccentric lever are connected to one another by the intermeshing teeth. Connecting the eccentric to the eccentric lever by the intermeshing teeth requires a high outlay on production and assembly and is susceptible to wear.
It is an object of the invention to provide an internal combustion engine and a connecting rod with low production and assembly costs, improved wear, and a low weight.